Mechanical linear actuators covert rotational motion into linear motion. One of the most common mechanical linear actuators is the screw-type mechanical linear actuator. In its most basic form, a screw-type mechanical linear actuator includes a nut member engaged with a screw member. Ball screws, acme screws and roller screws—common screw-type mechanical linear actuators—introduce ball bearings or rollers (e.g., moving through a ball race) to reduce friction between the nut member and the screw member or just plain unique thread in the case of acme screws. Regardless of the level of complexity of the screw-type mechanical linear actuator, rotation of the screw member about its longitudinal axis causes corresponding movement of the nut member along the longitudinal axis. Movement of the nut member along the longitudinal axis of the screw member may be in either a positive direction or a negative direction, depending on the direction of rotation of the screw member about the longitudinal axis.
In certain applications, it is necessary to physically limit the travel of the nut member of a screw-type mechanical linear actuator relative to the screw member. For example, an end stop may be positioned at the end of the screw member. When the nut member comes into physical contact with the end stop, the end stop may inhibit further axial movement of the nut member beyond the end stop.
In some cases, there is a need to have a separate mechanical end stop mechanism. Thrust reversers are one example, wherein the linear movement is by hydraulic pistons, but there is a need to have a separate mechanical end stop mechanism to stop the pistons before they reach their end of motion and can be damaged. Power drive units are another example, wherein the linear motion is only for the sake of stopping the surfaces in case of a system failure in order to prevent the surfaces from hitting the structure members.
Despite advances already made in the field, those skilled in the art continue with research and development efforts directed to multiple axis end stops for mechanical linear actuators.